Functional abdominal pain is defined as pain unrelated to an identifiable organic gastrointestinal disorder. The two subcategories of functional bowel disorders examined by this study will be RAP and IBS. The definition of RAP in children will follow Apley's classic definition of paroxysmal abdominal pain occurring in children between the ages of 4 and 16 years that persists for more than three months, with a frequency of three or more episodes of abdominal pain over a three month interval. A similar pattern of abdominal pain relieved by defecation and/or associated with altered bowel habits and/or stool consistency will be defined as IBS. Despite the above definitions, note that the typical frequency of pain episodes associated with functional bowel disorders is at least three times per month.